Over the past 10 years, phosphorus concentration trends are not significant at more than half (19 of 33) monitoring sites within the Bay watershed. Improving trends were estimated at 10 sites while degrading conditions were reported at 4 sites, indicating that in some locations, management actions, such as improved wastewater treatment and nonpoint-source pollution controls (i.e. urban stormwater runoff and agricultural runoff controls), have reduced phosphorus concentrations in streams.
The short-term flow-adjusted trends and yields indicator is calculated, and results and maps are published annually by the U.S. Geological Survey as part of a larger effort to determine loads and trends in nutrient and sediment concentrations and streamflow in the Chesapeake Bay watershed.